NEW YORK (Reuters Health) - Women who were exposed to air
pollution during pregnancy tended to give birth to slightly
lighter babies, in a new study from New York City.

A series of studies has suggested air pollution may be
harmful during pregnancy, but the issue remains unresolved.

"We had an opportunity to use a unique data resource in New
York City that was designed to estimate exposure throughout the
city, which allowed us to improve on past studies, as well as
examine a large, ethnically diverse population," David Savitz
told Reuters Health in an email.

Savitz, from the Alpert Medical School of Brown University
in Providence, Rhode Island, led the new study.

He and his colleagues looked at the birth weights of more
than 250,000 babies born in New York City hospitals during 2008
to 2010.

Using data from the New York City Community Air Survey, they
estimated how much pollution mothers had been exposed to during
pregnancy based on women's home addresses.

The researchers focused on particulate matter less than 2.5
micrometers in diameter, known as PM2.5, and nitrogen dioxide.

They found birth weights dropped by about 48 grams (less
than two ounces) for every 10 microgram per cubic meter increase
in particulate matter women were exposed to throughout their
pregnancies.

For each 10 parts per billion increase in nitrogen dioxide
exposure throughout pregnancy, birth weight was reduced by 18
grams, Savitz's team reported in the American Journal of
Epidemiology.

The U.S. Environmental Protection Agency (EPA) has set
national standards of 15 micrograms of PM2.5 per cubic meter on
average over the course of a year and 53 parts per billion of
nitrogen dioxide.

Another report from the New York survey found average
pollution levels were generally within those standards -
although they were measured slightly differently - but varied
widely.

The study doesn't prove air pollution was responsible for
the slight decreases and there are many factors that can
influence birth weight, the researchers noted.

The drops in birth weight don't point to any health concerns
at this time, but the numbers do suggest a potential for
problems, they said.

"While these are not important for any individual, on a
population level, if a large number of births are shifted by
that amount, there would be a real public health concern,"
Savitz said.

"The message really concerns policy, raising awareness that
even though we have reduced air pollution levels substantially,
there is still reason to believe that further reductions would
be beneficial and quite possibly, have a small beneficial effect
on the health of newborns," he said.

"It's really important to study air pollution because
everybody's exposed to it and that means all pregnant women are
exposed to it," Tracey Woodruff told Reuters Health.

She directs the Program on Reproductive Health and the
Environment at the University of California, San Francisco, and
wasn't involved in the new study.

The type of exposure measured in this study is not really
something that can be avoided because these tiny particles
easily travel indoors, Woodruff said. So the best way to reduce
exposure is to address the sources.

This type of pollution generally comes from combustion
sources, she said, like cars, trucks and power plants, and from
agricultural sources.

"The EPA has been putting out new regulations related to
particulate matter air pollution because PM is also associated
with a whole host of adverse health outcomes including mortality
and a number of respiratory and cardiovascular health problems,"
Woodruff said.

SOURCE: http://bit.ly/18lEbgl American Journal of
Epidemiology, online November 10, 2013.